This invention relates in general to photography and in particular to photographic elements provided with a magnetic stripe that is useful for sound recording. More specifically, this invention relates to photographic elements having a magnetic recording stripe overlying an antistatic layer, to a process for the manufacture of the aforesaid elements, and to a coating composition for use in the manufacture of the aforesaid elements.
It is well known to form magnetic recording stripes on photographic elements, such as motion picture films, and a variety of procedures have been developed to accomplish this objective. The magnetic recording stripe can be applied to the image-forming side of a photographic element, for example, it can be applied within a narrow groove formed within a silver halide emulsion layer. More typically, the magnetic recording stripe is applied to the side of the element opposite to the image-forming layer(s). Since photographic elements which require magnetic striping typically have a functional layer, such as an antihalation layer or an antistatic layer, on the side of the element opposite to the image-forming layer(s), the application of a magnetic recording stripe on this side presents a difficult problem. Thus, for example, localized removal of the functional layer to permit the striping composition to be applied directly to the support is usually impractical, whereas application over the functional layer frequently results in problems of inadequate bonding and resulting stripe separation.
Anti-halation layers which are located on the side of a photographic element opposite to the image-forming layer(s) are usually designed to be removed during processing of the element, and, accordingly, are comprised of a binder which is soluble in alkaline photographic processing solutions. Thus, if the magnetic stripe is applied over the anti-halation layer, it will be removed along with the anti-halation layer during processing unless suitable procedures are utilized to avoid such removal. Among the procedures which are known for this purpose is that of U.S. Pat. No. 3,220,843. As described in this patent, a magnetic stripe which is composite with the anti-halation layer and firmly adhered to the support so as to resist removal by alkaline photographic processing solutions can be formed by incorporating an N,N-dialkylamide in the magnetic striping composition. By use of the N,N-dialkylamide, the anti-halation layer is partially or completely dissolved in the region of the stripe and the striping composition is thereby able to reach the support and anchor thereto. A similar procedure is described in U.S. Pat. No. 3,647,541 in which the magnetic striping composition contains a combination of 2-methoxy ethanol and a dioxane. A different approach to the problem of applying a magnetic striping composition over an anti-halation layer is to incorporate in the magnetic striping composition an agent which is capable of reacting with the binder in the anti-halation layer to thereby insolubilize the anti-halation layer in the region of the stripe and prevent its removal in photographic processing solutions. This technique has been the subject of several patents, each of which relates to the use of particular insolubilizing agents; for example, the diazomethanes of U.S. Pat. No. 3,227,555, the compounds with reactive aldehyde groups of U.S. Pat. No. 3,840,374, the compounds having isocyanato or thioisocyanato groups of U.S. Pat. No. 3,870,525, the carbodiimides of U.S. Pat. No. 3,891,444, the m-benzene disulfofluorides of U.S. Pat. No. 3,999,992, and the combinations of bis-epoxides or polyepoxides with formamide or a sulfoxide of U.S. Pat. No. 4,008,088.
In the case where it is desired to apply a magnetic recording stripe over an antistatic layer which is on the side of the support opposite to the image-forming layer(s), the problem is somewhat different, since the antistatic layer is not usually intended to be removed during processing but rather is intended to be a permanent layer. However, it is frequently very difficult to achieve good adhesion of a magnetic stripe applied over an antistatic layer and, as a result, the stripe will often exhibit a tendency to separate from the element during handling and/or processing of the element. This is particularly the case with photographic elements in which the antistatic layer contains a phosphate ester which functions as an antistatic agent. Such use of phosphate ester antistatic agents is well known and is described, for example, in U.S. Pat. No. 3,658,573. The phosphate ester antistatic agents provide excellent antistatic protection to the photographic element, but typically make it very difficult to achieve good adhesion of an overlying magnetic stripe. Moreover, procedures which are effective in applying a magnetic striping composition over an anti-halation layer are generally ineffective when it is desired to stripe over the aforesaid phosphate-ester-containing antistatic layers; for example, the degree of adhesion may be inadequate or excessive curl in the region of the stripe may occur.
It is toward the objective of providing an improved composition and method for magnetic striping of photographic elements, in which the magnetic stripe is applied over an antistatic layer containing a phosphate ester which functions as an antistatic agent, that the present invention is directed.